128 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



Upper Miocene, or fourth group, a very small leaf described as Lomatia 

 microphylla, which even may belong to a species of Myrica. I have there- 

 fore until now considered as very doubtful the presence of true Proteacece iu 

 the geological floras of this continent, and for this reason I do not find any 

 fact in support of the hypothesis of a common origin and parallel develop- 

 ment of the Myrica and the Proteacece. On the contrary, I believe that the 

 deeper we go into the study of the fossil plants of North America, and 

 the more intimately we become acquainted with the characters of the ances- 

 tors of our present flora, the greater will we find to be the analogy of the old 

 types with the present ones, and that we shall see gradually disappear those 

 foreign types bearing the so-called Austro-Indian and Australian characters. 

 On the present subject, it seems established: that in Europe the Myricce 

 take a gradual and considerable importance during the whole Tertiary period, 

 and then nearly entirely disappear from the flora of that continent. Until 

 now, no species of this genus is described from the Pliocene. And per 

 contra: that in North America the representation of this group of plants is 

 scanty from the Cretaceous up to the Upper Miocene, where it takes that higher 

 degree of predominance which is preserved, it seems, in our present flora. 



I have formerly considered as referable to Myrica a fragment of a leaf, 

 remarkable indeed for its size, as a representative of a genus whose leaves 

 now are all of a comparatively small size. This leaf is by its form and ner- 

 vation in exact concordance of characters with those of Comptonia, as seen 

 from pi. Ixiv, fig. 1. The fragment is already much larger than Unger's 

 Myrica grandijlora, considered till now as the giant of the genus, and there- 

 fore its relation is contested on that ground. Now, the discoverer of this 

 fine specimen, taken from a shaft sixty feet deep, asserts that he has seen at 

 the same place leaves of the same kind of a far larger size, some of them 

 about ten feet in length. If so, we should have to look to another group of 

 plants for the relation of these leaves. I must, however, remark that, con- 

 trary to what is asserted by some paleontologists, the Tertiary leaves are 

 generally of a diminutive size in comparison with those of the flora of our 

 time. The size seems greatly exaggerated to the eyes by the fossilization, 

 or the flat position of the leaves upon stones, and is therefore considerably 

 reduced by measurements. The largest fossil dicotyledonous leaf which I 

 have ever seen is that of an Aralia, from the Upper Miocene of California, 

 appearing indeed of a monstrous size. It measures twenty-seven centimeters 



